What causes allergies?

Allergies are caused by the immune system's overreaction to certain substances, known as allergens. When a person with an allergy comes into contact with an allergen, their immune system mistakenly identifies it as harmful and releases chemicals, such as histamine, to fight it off. This results in symptoms such as itching, sneezing, and difficulty breathing. Common allergens include pollen, mold, dust mites, pet dander, and certain foods or even genetics.